Perhaps you should try some spelling variations:
trung quang » truong quang, trong quang, trung quan
thanh trung » thanh tung
quang trong » quang truong, quang trung, quan trong
hieu quang » thieu quang, hieu qua, diep quang
chieu sang » chieu sach, chieu xanh, hieu lang
hieu quan » hieu qua, lieu quan, thien quan
cong dan » cong san, cong tan, huong dan
dan toan » van toan, dan than, manh toan
toan cau » toan cao, toan ban, toan tap

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((((hieu quang) OR (hieu quan))) or (chieu sang)) - thanh trung quang trong cong dan toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((((hieu quang) OR (hieu quan))) OR (chieu sang)) - thanh trung quang trong cong dan toan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((((hieu quang) OR (hieu quan))) or (chieu sang)) - thanh trung quang trong cong dan toan cau".
• Adding a wildcard symbol may retrieve word variants: hoc ((((hieu quang) OR (hieu quan))) or (chieu sang)) - thanh trung quang trong cong dan toan cau*.